Resource cleanup
Resource cleanup is the release of resources or restoration of state when an operation or scope ends or fails.
React Quickly, Second Edition
A cleanup function is a function associated with an effect that releases resources or reverses external interactions when the effect is no longer active.
- How it is used
- Stops timers, removes event listeners, and guards pending requests when a component or its effect is no longer active.
- How deep it goes
- Works through mount, unmount, and dependency-change timing with component examples, including cleanup-only effects.
- Examples
- Uses a stopwatch, pauseable countdown, window-size display, remote data request, and dialog.
- What you can do after
- Build it from scratch in React components that stop intervals and remove listeners at the right time.
Read how React Quickly, Second Edition explains resource cleanup →
Modern C, Third Edition
Cleanup is the release or restoration of resources and state needed when an operation completes or fails.
- How it is used
- Applies cleanup to error-handling paths, dynamic allocation, preserved errno, and normal program termination.
- How deep it goes
- Works through allocation, reallocation, output failure, centralized goto cleanup, errno restoration, and atexit handlers.
- Examples
- Uses number-printing functions, malloc and realloc failures, fputs errors, error_cleanup, goto, and an atexit greeting handler.
- What you can do after
- Apply centralized cleanup to C error paths and register termination handlers with atexit when appropriate.
Read how Modern C, Third Edition explains resource cleanup →
The Art of Code
Resource cleanup is the release or closure of acquired computing resources after an operation finishes or fails.
- How it is used
- Uses resource cleanup as an ending check during method review and narrative refactoring.
- How deep it goes
- Frames cleanup as a review question and names resource examples, but does not specify implementation mechanisms.
- Examples
- Uses files, connections, sockets, and a long-method rewriting exercise as concrete cleanup examples.
- What you can do after
- Evaluate method endings for clear outcomes and properly cleaned-up resources.
Modern C
Cleanup code is code that releases resources and restores required state when an operation completes or fails.
- How it is used
- Handles allocation and error paths in C functions that must release resources reliably.
- How deep it goes
- Explains shared cleanup control flow and three goto rules, but stops short of broader nonlocal-jump mechanisms.
- Examples
- Uses an optimized number-printing function handling buffer growth, allocation failure, and INT_MAX overflow.
- What you can do after
- Apply it via C's goto to centralize cleanup while keeping ordinary control flow readable.
React in Depth
A cleanup function is a function returned by a React effect to undo or release resources created by that effect.
- How it is used
- Uses effect cleanup to release timer resources and keep repeated effect execution safe during development.
- How deep it goes
- Defines the return contract, demonstrates interval teardown, and traces cleanup ordering; it does not generalize beyond focused effect examples.
- Examples
- Uses a running timer, clearInterval, invalid boolean returns, and console logs from repeated Strict Mode effects.
- What you can do after
- Diagnose TypeScript effect-return errors and implement interval cleanup with a valid React effect return.
D3.js in Action, Third Edition
A cleanup function is a function returned from a React effect to release resources or prevent work after the effect is no longer active.
- How it is used
- Protects React data-fetching components from state updates after unmounting.
- How deep it goes
- Demonstrates a mounted-flag pattern but does not compare alternative cleanup strategies.
- Examples
- Uses a D3 JSON request that updates loading and data state through a guarded Promise callback.
- What you can do after
- Apply it via React useEffect to prevent updates from an unfinished D3 request after unmounting.
Read how D3.js in Action, Third Edition explains resource cleanup →
Related concepts
- useEffectused by · useEffect is a React Hook that runs effect logic after rendering to synchronize a component with external systems and optionally perform cleanup.
- handleruses · A handler is a callable or software component that processes an event, request, message, or other input and performs associated processing.
- timeraddresses · A timer is a hardware or software mechanism that tracks time and triggers an event or action after a specified duration or at scheduled intervals.
- gotoimplemented by · A goto statement or instruction unconditionally transfers program execution to a labeled statement or location within the current execution unit.
- deferaddressed by · Defer is a language feature that schedules an operation to execute when the surrounding function or scope exits, including during exceptional unwinding.
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